1. Field of the Invention
The present invention relates to wireless communication, and more specifically, to a method and apparatus that report a measurement result in a wireless communication system.
2. Related Art
3GPP (3rd generation Partnership Project) LTE (Long Term Evolution), which is an advanced version of UMTS (Universal Mobile Telecommunications System), is not being introduced as 3GPP release 8. 3GPP LTE uses OFDMA (orthogonal frequency division multiple access) on downlink and SC-FDMA (Single Carrier-frequency division multiple access) on uplink. 3GPP LTE adopts MIMO (Multiple Input Multiple Output) having a maximum of 4 antennas. Recently, 3GPP LTE-A (LTE-advanced) which is an advanced version of 3GPP LTE is now in discussion.
GPP LTE-A adopts technologies, such as carrier aggregation and relays. A 3GPP LTE system is a single carrier system that supports only one bandwidth (i.e., a single element carrier) of {1.4, 3, 5, 10, 15, 20} MHz bandwidths. However, LTE-A introduces a multi-carrier using carrier aggregation. The component carrier is defined with a center frequency and a bandwidth. The multi-carrier system uses a plurality of component carriers having a bandwidth smaller than the entire bandwidth.
A user equipment continues to perform measurement so as to maintain quality of a radio link with a serving cell receiving a service. A cell or a frequency, as a target for measurement, is referred to as a measurement object, and each measurement object is associated with a report configuration that independently induces a report of a measurement result. The user equipment performs measurement on the measurement targets, and if the report configuration is met, reports the measurement result to a base station.
As a multi-carrier is introduced, there may be a plurality of serving cells. If the user equipment reports measurement results for all of the plurality of serving cells to the base station, the base station may set an optimum cell to the terminal as a serving cell based on various types of information. However, radio resources in reporting the measurement result may be restricted and the measurement results of all the serving cells are not always information required for the base station.